Objective: To evaluate the prevalence and severity of hyperprolactinemia among a large sample of patients with schizophrenia and related psychotic disorders treated with typical and atypical antipsychotic medications.

Method: Three electronic databases (general medical, psychiatric, and pharmacologic) containing the census data from November 2002 through March 2003 for a state-funded, inpatient hospital serving the chronically mentally ill were merged (N = 470). This database was purged of patient names, while the unique hospital identification number and demographic variables in each record were retained. These records were then screened to exclude patients with medications (except neuroleptics) or medical conditions known to elevate or suppress prolactin, leaving an overall sample (N = 422) in which to evaluate the prevalence of hyperprolactinemia. The sample was composed of patients with DSM-IV schizophrenia (N = 213), other related psychotic disorders (N = 131), mood disorders (N = 44), and other disorders (N = 34).

Results: For the overall sample (N = 422), which combined men and women, the mean serum prolactin level was 41.5 ng/mL; 290 of 422 patients were above the normal range. For women (N = 133), the mean serum prolactin level was 57.9 ng/mL, and 67% had levels above normal. For men (N = 289), the mean level was 33.9 ng/mL, with a 70% prevalence of hyperprolactinemia. While age did not influence the prevalence of elevated prolactin among men, age (reflecting reproductive status) was a significant variable in women; older age was associated with lower prolactin levels. For the study sample, a highly significant correlation was observed between neuroleptic dose (chlorpromazine equivalent) and serum prolactin level; however, this relationship was not determined on a medication-by-medication basis. Medications known to elevate prolactin were associated with higher prevalence rates of hyperprolactinemia, and "prolactin-sparing" medications had lower prevalence rates. However, when they were used in combination, the prolactin-elevating medication overwhelmed the effects of prolactin-sparing medication.

Conclusions: This study suggested that neuroleptic treatment of schizophrenia is strongly associated with hyperprolactinemia and showed important differences between prolactin-sparing and prolactin-elevating medications.